The present invention relates to a process and apparatus for machining an electrode workpiece by electrical discharges occurring in a machining gap between the electrode workpiece and an electrode tool, the electrode workpiece and the electrode tool being relatively displaced along an axis of feed of the electrode tool into the workpiece and simultaneously along a translation path in a direction perpendicular to the feed axis, the translation motion being controlled from the moment at which machining starts such as to maintain a predetermined machining gap between the electrode workpiece and the electrode tool.
It is known to displace the electrode tool of an EDM machine along a translation motion path relative to the electrode workpiece for the purpose of effecting an even multi-directional enlargement of the electrode tool, using the same electrode tool for rough and finish cuts of the workpiece, while improving the machining fluid flow through the machining gap. However, when the translation, or orbiting, motion is along a circular path, sharp angles of the active surface of the electrode tool cannot be reproduced on the workpiece except with a curvature equal to the radius of the circular motion. If the workpiece must be provided with sharp angles it has been found desirable to effectuate sequentially a series of radial translations of constant amplitudes starting from a central position and in directions uniformly distributed angularly over a complete circle. Such a process, which is disclosed in French Pat. No. 1,274,953, presents the inconvenience, however, of preventing a simultaneous control of the axial and radial progression of machining, and of preventing maintaining an average current of high intensity in view of the regular and synchronous progression of the radial direction of the translation motion.
Another process permitting radial machining, disclosed in U.S. Pat. No. 4,104,501 assigned to the same assignee as the present application, consists in causing the electrode tool to effectuate a series of slanted translations in predetermined directions, relative to the axis of penetration of the electrode tool into the workpiece, such as to control simultaneously the radial and axial machining feed in each of those directions. However, this method, as well as the above-mentioned method, causes the apparition of ineffective time intervals during which machining current is cut-off, resulting in substantially decreasing the intensity of the average machining current.